Z86D990 Datasheet, PDF (66/102 Pages) Zilog, Inc. – Low-Voltage Micro controllers with ADC

Z86D990/Z86D991 OTP and Z86L99X ROM
Low-Voltage Microcontrollers with ADC
59
Stack Pointer (SP)
The Z86D99/Z86L99 family of products is configured for an internal stack. The
size of the stack is limited only by the available memory space or general-purpose
RAM registers dedicated to this task. An 8-bit stack pointer, as described in
Table 17, is used for all stack operations.
Table 17. SP Register [Group/Bank F0h, Register F (R255)]
Bit
7
6
5
4
Bit/Field Stack Pointer
R/W
R/W R/W R/W R/W
Reset
X
X
X
X
R = Read, W = Write, X = Indeterminate
Bit
Position
Bit/Field
R/W Value
76543210 Stack Pointer R/W X
3
2
1
0
R/W R/W R/W R/W
X
X
X
X
Description
Points to the data stored on the top of
the stack; an overflow or underflow
can occur if the stack address is
incremented or decremented during
normal stack operations
PS003807-1002
PRELIMINARY